U.S. Pat. No. 3,880,302, describes an apparatus for charging a shaft furnace which comprises two locks placed next to one another and operating alternately. This known charging installation is supported by a relatively large framework which is itself carried by a square tower installed round the furnace. The distributor chute is suspended on the diametrically opposed axles of two drive housings revolving round the vertical axis under the action of the first running ring. Each of these housings is connected to the second running ring by means of several pinions and gears, in order to change the inclination of the chute relative to the axis of the furnace. The distributor chute, the inner lining of which has to be regularly renewed, can be replaced by means of a handling device of the type described in the U.S. Pat. No. 4,729,549. According to this patent, the chute is extracted laterally through an orifice made in the upper conical part of the furnace wall.
This charging installation and the mechanism for driving the chute have proved especially effective and advantageous for use on new blast furnaces or for major repairs and since the initial design of this charging installation it has equipped many blast furnaces.
Unfortunately, it has been impossible for this installation of very high performance on blast furnaces of large size, to be adapted with similar success to blast furnaces of smaller size, especially those without a square tower. In this type of furnace, the charging installation and the work platform surrounding it are supported directly by the all of the furnace. Unless reinforcements are provided beforehand as a result of major costly conversions, it is therefore impossible to dismount the distributor chute in the way proposed in the above mentioned document, since an orifice cannot be made in the furnace wall and in the work platform to avoid reducing their stability and resistance.
To avoid having to pierce the wall of the furnace in order to dismount the chute, Luxembourg Patent Application No. 87,219 (copending commonly assigned U.S. patent application, Ser. No. 382,517, filed July 19, 1989, now U.S. Pat. No. 4,941,792), proposed to dismount the chute upwards through the casing of its drive mechanism. Despite this solution, there is still the problem that the installation is supported by the furnace wall. In fact, it is well known that the furnace wall experiences thermal expansion movements and this consequently has an effect on the casing of the drive mechanism of the chute, this therefore being exposed to risks of deformation. Now the drive mechanism known from U.S. Pat. No. 3,880,302, comprising a complex system of gears and pinions, especially in the region of the two rotary housings generating the pivoting of the chute, does not tolerate deformations of this extent.
Moreover, when a conventional bell-type charging device of an existing furnace is to be replaced by a modern charging apparatus with a rotary distributor chute, the problem of availability of space arises. In fact, the new apparatus has to be arranged between the supporting collar of the lower bell and the installation for raising the charging material, this usually being a skip transporter. Unfortunately, this available space is often very limited and it is therefore difficult to provide a charging installation of the above described type in it.